Diolefins from chloroethers

ABSTRACT

In the production of diolefins by reaction of a halo ether and an olefin followed by cracking hydrogen halide and alcohol from the intermediate adduct, olefin ethers are formed in the cracking reactor and are isolated by conventional distillation and recycled to the cracking reactor to be converted to diolefins and alcohol.

United States Patent inventors Appl. N 0.

Filed Patented Assignee DIOLEFINS FROM CHLOROETHERS 10 Claims, 1 DrawingFig.

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Findlay, Ohio John R. Coleman, Jr. [50] Field of Search 260/681Littleton; David W. Hall, Englewood; Frank L. Referellces Cited Dormish,Denver, all of Colo. UNITED STATES PATENTS 861,108 3,360,583 12/196711611 et al. 260/681 Sept- 25, 1969 3,377,405 4/1968 Hurley et al.260/681 Sept. 21, 1971 Marathon on Company Primary Exammer- Delbert E.Gantz Assistant Examiner-G. E. Schmitkons Attorneys.loseph C. Herring,Richard C. Willson and Jack L.

Hummel ABSTRACT: In the production of diolefins by reaction of a haloether and an olefin followed by cracking hydrogen halide 260/681, an alh l r m he in rm i adduct, fin he are 260/616 formed in the crackingreactor and are isolated by conven- C07c 1/20, iona dis illation andrecycled to the cracking reactor to be COj 41/12 converted to diolefinsand alcohol,

CRUX ISOPREAE CNBK o MAKE-UP 25 NMP NMP-HCI i 22 32 l9 l NMP MAKE-UP 6TARS NMP RECYCLE OLEFINS ETHERS RECYCLE 8 HCI RECYCLE l 26 CRUDEISOPRENE METHYLCHLORIDE '4 POLYMERlZATION GRADE ISOPRENE CH OH RECYCLE 2PATENTEI] SEPZI I97! 3.607.965

I CRUDE ISOPRENE CMBLE K) MAKE-UP NMP NMP

MAKE-UP 6 TARS NMP RECYCLE OLEFINS ETHERS RECYCLE HCI RECYCLE 2s CRUDEISOPRENE METHYLCHLORIDE 4 POLYMERIZATION GRADE ISOPRENE CH-30H RECYCLE2o lzwavrms .m. COLEMAN JR. 0w HALL F. 1.. oonmsn ATTORNEY SUMMARY OFTHE INVENTION This invention relates to the production of diolefins,e.g., the process described in US. Pat. No. 3,360,583. In the process ofthat patent, conjugated dienes are prepared by reacting alpha haloethers with olefins and splitting out a hydrogen halide and alcohol fromthe resulting halo ether adduct. The patent broadly sets forth usefulstarting materials and reaction conditions for the process. In general,the halo ethers are substituted in the alpha position with chloro,bromo, or iodo and are methyl, ethyl, or propyl symmetrical orunsymmetrical alphahalo ethers. Examples include: bis (chloromethyl)ether, dichloromethyl methyl ether, and chloromethyl methyl ether. Thereactive olefins are also broadly set forth and includehalogen-substituted olefins. Examples of olefins include allyl chloride,l-butene, isobutylene, and preferably olefins having from 2 to 9 carbonatoms. A petroleum fraction containing a mixture of olefins, such as a Cfraction, is also useful in the process. The adduction of the haloetherto the olefin is generally carried out in the presence of aFriedel-Crafts catalyst at a temperature of 30 to 70 C, preferably fromto 35 Once the halo ether adduct has been prepared by reaction of thealpha halo ether with the olefin in the presence of a catalyst, the haloether adduct is pyrolyzed at from 90 to 350 C., preferably from 120 to180 C. to form a desired conjugated polyene. This pyrolysis reaction isadvantageously carried out in the presence of a basic tertiary amidesolvent, such as N-methyl-Z -pyrrolidone. In general, the solventscontain nitrogen and have base or dissociation constants (Kg-of lessthan about l l0, preferably between and 10, as measured in aqueoussolutions at -25 C. In the alternative, the pyrolysis or crackingoperation may desirably be conducted in the presence of a suitablemolecular sieve catalyst.

Conjugated diolefins, trienes, and higher polyenes, made in accordancewith the above process have found increasing use in the elastomer andinsecticide industries. A particularly preferred product is isoprene, avaluable monomer in the production of polyisoprene for use in the rubberindustry.

The present invention is essentially an improvement of the processdescribed in U.S. Pat. No. 3,360,583, described above. In that process,up to 100 percent conversions are obtained when relatively severeoperating conditions, e.g., high pyrolysis temperatures, are employed.However, to protect the desired polyolefin product, it is oftennecessary to employ milder operating conditions, with the result thatpyrolysis of the intermediate adduct is incomplete. Rather, a class ofmaterials known as olefin ethers is produced by the partial cracking ofthe intermediate adduct. The splitting of the hydrogen halide isessentially complete, but the splitting of the alcohol is not alwayscomplete, producing the olefin ether byproduct. The conjugateddiene-product mixture will contain generally from about 1 to up to 10weight percent of these olefin ethers, which comprise an unwantedbyproduct as well as a loss of valuable reactants.

SUMMARY OF THE INVENTION We have found that by distillation methods theolefin ethers may be recovered separately from the product mixture.Recycling the olefin ethers back to the cracking reactor converts themto the desired conjugated diene product. In this manner, the overallconversion of reactants to desired diene products is greatly enhanced ina continuous type process.

PREFERRED EMBODIMENTS OF THE INVENTION In a particular embodiment of theinvention, in the preparation of isoprene, reference is made to theaccompanying drawings, wherein:

The figure is a continuous process flow diagram for the production ofisoprene using N-methyl-pyrrolidone (NMP) as the cracking solvent.

Referring to the figure, 3-chloro-3-methylbutyl methyiether CMBME),prepared by reaction of chloromethyl methyiether with isobutylene in thepresence of titanium tetrachloride, identified as stream 2 is charged tocracking reactor 4. The feed to the cracking reactor includes crackingsolvent NMP, recycled NMP 6, and recycled olefin ethers 8. The-reactionis carried out at 230 F. The reaction rate may be enhanced by includingmetal halide catalysts in reactor 4, such as zinc chloride and lithiumchloride. Overhead temperature of reactor 4 is controlled at F. Most ofthe partially cracked olefin ethers condense and flowback into thereactor, while isoprene and methyl alcohol escape in overhead streamit). At least about 1 and up to about 10 weight percent of overheadstream 10 include the partially cracked olefin ethers, which consistmostly of 3-methyl-3-butenyl methyiether and 3methyl-2-butenylmethyiether.

Overhead stream 10 containing isoprene together with methyl alcohol, anytertiary butyl chloride passing through the cracking reactor unchanged,methyl chloride, olefin ethers, and some unreacted isobutylene entersproduct separation column 12 (a conventional distillation column) wherethe more volatile components are stripped at F. from the more volatileolefin ethers. The olefin ethers are recycled 8 to reactor 4 forcracking to isoprene and methyl alcohol. Overhead stream 14 containingthe crude isoprene is further stripped of methyl chloride infractionator l6 and of the bulk of the methyl alcohol present infractionator 18. The methyl alcohol is recycled 20 to a chloromethylmethyl ether synthesis step, not shown. Any methyl alcohol whichcodistills with the isoprene overhead may be removed by various methods,e.g., using a conventional water scrubbing step, and combined withstream 20 for recycle.

The isoprene product, which contains a percent or so of impurities, maybe percolated through a molecular sieve absorber to raise the puritylevel to 99+percent.

The cracking solvent is recovered from reactor 4 as stream 33 in theform of NMP'HCI dissolved in NMP. Various separation techniques may beemployed to recover the solvent for recycle, such as by the method ofcopending application Ser. No. 725,206, filed Apr. 29, 1968. Stream 22also contains HC], tar water, etc. in addition to NMP. Stream 22 isheated in packed column 24 to decompose the NMPHCI to give an overheadstream 26 containing HCl and water. A portion of bottom stream 28 issteam stripped in column 30 to separate NMP overhead for recycle fromthe tars formed. Any water present in the NMP overhead stream ispreferably split out to purify the NMP for recycle.

As an alternative embodiment, CMBME can be charged to a molecular sievecracking reactor. Various acidic oxide cracking catalyst systems may beemployed, exemplified by SK-SOO molecular sieves manufactured by theNorton Company, 10X manufactured by the Union Carbide Corporation,silicon aluminum, bentonite, silica gel, silica-magnesia, natu ralclays, or various other catalysts on an inert catalyst support. Any ofthe catalysts described in U.S. Pat. No. 3,360,583 may be employed.

The polyene product, hydrogen halide and alcohol emanating from thepyrolysis reactor may be recovered by any suitable method. It will beappreciated by those skilled in the art that any recovery methodsuitable for recovery of products from vapor phase type operations maybe employed. Suitably, the product vapors may be processed in a waterscrubber. The hydrogen halide and alcohol are recovered from the scrubwater along with olefin ethers to be recycled to the pyrolysis reactor.Any tertiary alkyl halides produced during pyrolysis may be cracked andrecycled according to the method of copending application Ser. No.86l,100. Nonvolatile organic materials, such as excess halo ether-olefinadduct feed may be condensed during the water scrubbing operation andremoved as a separate liquid phase and recycled. The volatilecomponents, such as the desired polyene product and the small amounts ofalkyl halides formed by the reaction of portions of the hydrogen halideand alcohol may either be condensed in receiver.

Other variations and modifications of the invention will become apparentto those skilled in the art upon a reading of 5 the specification andclaims and such are to be included within the scope of the inventiondefined in the specification and appended claims.

What is claimed is:

l. A process for preparing diolefin compounds comprising reacting analpha halo ether with a reactive olefin to form a halo ether adduct ofthe olefin, splitting hydrogen halide and alcohol from the halo etheradduct to form a diolefin compound and olefin ethers of the halo etheradduct, recycling at least a portion of said olefin ethers of the haloether adduct to the splitting step, and recovering the diolefiniccompound.

2. A process for preparing conjugated diene compounds comprisingreacting an alpha halo ether with a reactive olefin in the presence ofan Friedel-Crafts catalyst at temperatures ranging from about 30 toabout 70 C. to form a halo ether adduct of the olefin, splittinghydrogen halide and alcohol from the halo ether adduct at temperaturesranging from about 50 to about 500 C. to form polyene and olefin of thehalo ether adduct, separating hydrogen halide from the diene and olefinether of the halo ether adduct, recycling at least a portion of theolefin ether of the halo ether adduct to the splitting step, andrecovering the diene substantially as formed.

3. The process of claim 2 wherein the splitting of the halo ether adductis effected in the presence of a tertiary amide solvent.

4. The process of claim 3 wherein the solvent is N-methyl-2-pyrrolidone.

5. The process of claim 2 wherein the halo ether adduct is split in thepresence of an acidic oxide catalyst supported on a fixed bed.

6. The process for the preparation of isoprene comprising reactingchloromethyl methyl ether with isobutylene in the presence of a catalystat temperatures of from about 0 to about C., to form3-chloro-3-methylbutyl methylether, splitting isoprene therefrom at fromabout 50 to about 500 C., and forming olefin ethers of the3-chloro-3-methylbutyl methylether adduct, recycling the olefin ethersformed to the splitting step for conversion to isoprene and methylalcohol, and recovering isoprene.

7. The process of claim 6 wherein splitting of the ether is accomplishedin the presence of a tertiary amide solvent.

8. The process of claim 7 wherein the solvent is N-methyl-2-pyrrolidone.

9. The process of claim 6 wherein the 3-chloro-3-3-methylbutylmethylether is split in the presence of an acidic oxide containingmolecular sieve catalyst.

10. The process of claim 6 wherein the olefin ethers comprisesubstantially 3-methyl-3-butenyl methylether and 3- methyl-Z-butenylmethylether.

WW UMTED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,607,965 Dated Sept. LL 1971 Inventofls) JOHN R. COLEMAN, JR. ET AL Itis certified that error appears in the above-identified patent and thatsaid Letters Patent are hereby corrected as shown below:

C01. 1 line 3 Delete "SUMMARY OF INVENTION" Insert --BACKGROUND OFINVENTION- Col. 1, line 23: After "catalyst" insert --such as titaniumtetrachloride or zirconium tetrachloride.

Col. 1, line 33: Delete "1x10 and insert --lxl0 Col. 1, line 34: Delete"lo fi' and "lo g na insert -10 and -l0 Col. 2, line 2 Insert before"CMBME" Col. 4, line 22: Delete "3-chloro3-3methyl" and insert-3-chloro3methyl--.

Signed and sealed this 21 st day of March 1972.

(SEAL) Attest:

M,FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK Commissioner ofPatents

2. A process for preparing conjugated diene compounds comprisingreacting an alpha halo ether with a reactive olefin in the presence ofan Friedel-Crafts catalyst at temperatures ranging from about -30* toabout 70* C. to form a halo ether adduct of the olefin, splittinghydrogen halide and alcohol from the halo ether adduct at temperaturesranging from about 50* to about 500* C. to form polyene and olefin ofthe halo ether adduct, separating hydrogen halide from the diene andolefin ether of the halo ether adduct, recycling at least a portion ofthe olefin ether of the halo ether adduct to the splitting step, andrecovering the diene substantially as formed.
 3. The process of claim 2wherein the splitting of the halo ether adduct is effected in thepresence of a tertiary amide solvent.
 4. The process of claim 3 whereinthe solvent is N-methyl-2-pyrrolidone.
 5. The process of claim 2 whereinthe halo ether adduct is split in the presence of an acidic oxidecatalyst supported on a fixed bed.
 6. The process for the preparation ofisoprene comprising reacting chloromethyl methyl ether with isobutylenein the presence of a catalyst at temperatures of from about 0* to about70* C., to form 3-chloro-3-methylbutyl methylether, splitting isoprenetherefrom at from about 50* to about 500* C., and forming olefin ethersof the 3-chloro-3-methylbutyl methylether adduct, recycling the olefinethers formed to the splitting step for conversion to isoprene andmethyl alcohol, and recovering isoprene.
 7. The process of claim 6wherein splitting of the ether iS accomplished in the presence of atertiary amide solvent.
 8. The process of claim 7 wherein the solvent isN-methyl-2-pyrrolidone.
 9. The process of claim 6 wherein the3-chloro-3-3-methylbutyl methylether is split in the presence of anacidic oxide containing molecular sieve catalyst.
 10. The process ofclaim 6 wherein the olefin ethers comprise substantially3-methyl-3-butenyl methylether and 3-methyl-2-butenyl methylether.